In power transmission networks alternating current (AC) power is typically converted to direct current (DC) power for transmission via overhead lines and/or under-sea cables. This conversion removes the need to compensate for the AC capacitive load effects imposed by the transmission line or cable and reduces the cost per kilometre of the lines and/or cables, and thus becomes cost-effective when power needs to be transmitted over a long distance.
HVDC converters are used to convert between AC power and DC power and such converters are one example of an electrical equipment item that incorporates one or more power semiconductor modules, although other electrical equipment items may also do so. Typically such power semiconductor modules include one or more semiconductor switching elements, e.g. in the form of Insulated Gate Bipolar Transistors (IGBTs) or chain-link sub-modules, and in HVDC converters they are a key component as the semiconductor switching elements therein act as controlled rectifiers to convert AC power to DC power and vice versa.